From: Andrew Morton <akpm@osdl.org>

Use page_mapping(), not page->mapping.

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Christoph Lameter <clameter@engr.sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---

 mm/rmap.c |   12 +++++-------
 1 files changed, 5 insertions(+), 7 deletions(-)

diff -puN mm/rmap.c~tracking-dirty-pages-in-shared-mappings-v4-fix3 mm/rmap.c
--- devel/mm/rmap.c~tracking-dirty-pages-in-shared-mappings-v4-fix3	2006-05-11 08:09:39.000000000 -0700
+++ devel-akpm/mm/rmap.c	2006-05-11 08:09:39.000000000 -0700
@@ -465,9 +465,8 @@ out:
 	return ret;
 }
 
-static int page_wrprotect_file(struct page *page)
+static int page_wrprotect_file(struct address_space *mapping, struct page *page)
 {
-	struct address_space *mapping = page->mapping;
 	pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
 	struct vm_area_struct *vma;
 	struct prio_tree_iter iter;
@@ -476,12 +475,10 @@ static int page_wrprotect_file(struct pa
 	BUG_ON(PageAnon(page));
 
 	spin_lock(&mapping->i_mmap_lock);
-
 	vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
 		if (VM_SharedWritable(vma))
 			ret += page_wrprotect_one(page, vma);
 	}
-
 	spin_unlock(&mapping->i_mmap_lock);
 	return ret;
 }
@@ -492,9 +489,10 @@ int page_wrprotect(struct page *page)
 
 	BUG_ON(!PageLocked(page));
 
-	if (page_mapped(page) && page->mapping) {
-		if (!PageAnon(page))
-			ret = page_wrprotect_file(page);
+	if (page_mapped(page)) {
+		struct address_space *mapping = page_mapping(page);
+		if (mapping)
+			ret = page_wrprotect_file(mapping, page);
 	}
 
 	return ret;
_